1. Field of the Invention
The present invention relates to hard films and sputtering targets for the deposition thereof. Specifically, it relates to hard films that have excellent lubricity at high temperatures, show excellent wear resistance and can improve the wear resistance and oxidation resistance of cutting tools such as tips, drills, and end mills, and plastic working jigs such as dies. It also relates to sputtering targets for use as evaporation sources in the deposition of the hard films.
2. Description of the Related Art
For improving wear resistance of cutting tools, hard films such as TiN, TiCN, or TiAlN are applied to base materials such as hard metal (cemented carbide), cermet, or high-speed tool steel. In particular, multicomponent (carbo)nitride films of titanium and aluminum such as TiAlN films and TiAlCN films (hereinafter referred to as “TiAl hard films”), as disclosed in Japanese Patent No. 2644710, exhibit excellent wear resistance, and they are suitably applied to cutting tools for high-speed cutting operation or for cutting materials with high hardness such as hardened steels. However, further demands have been made to provide hard films with more excellent wear resistance with increasing hardness of materials to be cut or increasing speed of cutting operation.
Japanese Unexamined Patent Application Publication (JP-A) No. 2004-100004 discloses a film containing (Tia, Wb)(Cx, Ny)z, wherein “a”, “b”, “x”, and “y” are molar ratios and satisfy the following conditions: 0.6≦a≦0.94, 0.06≦b≦0.4, a+b=1, 0.1≦x≦0.9, 0.1≦y≦0.9, and x+y=1; and “z” is the total molar ratio of nonmetallic elements to metallic elements and satisfies the following condition: 0.8≦z≦1. Disclosed examples of the film are (Ti, W)C, (Ti, W, Nb)C, (Ti, W, Ta)C, (Ti, W, Ta, Nb)C, (Ti, W, Al)C, (Ti, W, Si)C, (Ti, W) (C, N), (Ti, W, Nb) (C, N), (Ti, W, Ta) (C, N), (Ti, W, Ta, Nb) (C, N), (Ti, W, Al) (C, N), (Ti, W, Si) (C, N), (Ti, W)N, (Ti, W, Nb)N, (Ti, W, Ta)N, (Ti, W, Ta, Nb)N, (Ti, W, Al)N, and (Ti, W, Si)N. The document also discloses a film represented by (Tia, Wb, Mc) (Cx, Ny)z, wherein M is at least one element selected from Al, Si, Zr, Hf, V, Nb, Ta, Cr, and Mo; “a”, “b”, “x”, and “y” are molar ratios and satisfy the following conditions: 0.6≦a≦0.94, 0.06≦b≦0.4, 0≦c≦0.1, a+b+c=1, 0.1≦x≦0.9, 0.1≦y≦0.9, x+y=1; and “z” is the total molar ratio of the nonmetallic elements C and N to the metallic elements Ti, W, and M and preferably satisfies 0.8≦z≦1. It mentions that at least one element selected from Al, Si, Zr, Hf, V, Nb, Ta, Cr, and Mo maybe contained in the hard-metal base material or film. However, the W-containing film is used as an interlayer for improving the adhesion between TiN or TiCN and the hard-metal base material, and the document fails to describe the mechanical properties and lubricity of this layer.